KR20160048903A - High temperature superconductor tape with alloy metal coating - Google Patents

Abstract

In one embodiment, a superconductor tape comprises a substrate comprising a plurality of layers, an oriented superconductor layer disposed over the substrate, and an alloy coating disposed over the superconductor layer, wherein the alloy coating comprises one or more metal layers and comprises at least one metal The layer comprises a metal alloy.

Description

HIGH TEMPERATURE SUPERCONDUCTOR TAPE WITH ALLOY METAL COATING BACKGROUND OF THE INVENTION [0001]

The present embodiments relate to superconducting materials, and more particularly, to superconducting tapes and their manufacturing techniques.

Superconducting wires or tapes have been developed based on high temperature superconducting (HTc) materials that can have a critical temperature TC of at least 77 K and enable their use in cryogenic systems that are cooled by liquid nitrogen. In some applications, such as in a superconducting fault current limiter (SCFCL), high temperature superconducting (HTS) tapes can experience high temperature excursion in the event of a superconducting layer undergoing a transition to a non-superconducting state have.

Due to the limited resistance acquired by the superconducting layer when a fault occurs in the SCFCL, the current that is almost exclusively conducted through the superconductor layer under the normal operation of the SCFCL results in a lower resistance than the superconductor layer, typically a current-resistant superconductor layer Lt; RTI ID = 0.0 > metal layers < / RTI > The current passing through the metal layers during a fault condition can cause resistive heating to produce temperatures up to 400 DEG C or higher on the HTS tape. As a result of the high temperatures, oxidation may occur at the local spots or at the metal layer interface as well as roughening of the metal surfaces leading to degradation of the metal layers and reduction of the lifetime of the HTS tape.

On the other hand, for the effect of a significant voltage drop along the length of the superconductor tape, it may be desirable to increase the sheet resistance of the metal layers on the HTS tape. Although this can in principle be achieved by reducing the thickness of the metal layer, such as copper, the reduced thickness can lead to other performance degradations or increased susceptibility to agglomeration which can shorten the HTS tape life. These improvements are about the various considerations that are required.

This summary is provided to introduce a selection of concepts, which are further described in the following detailed description, in a simplified form. This summary is not intended to identify key features or key features of the claimed subject matter, nor is it intended as an aid in determining the scope of the claimed subject matter.

In one embodiment, a superconducting tape comprises a substrate comprising a plurality of layers, an oriented superconductor layer disposed over the substrate, and an alloy coating disposed over the superconductor layer, wherein the alloy coating comprises one or more metal layers The at least one metal layer comprises a metal alloy.

In a further embodiment, a method of forming a superconductor tape comprises forming a superconductor layer comprising a superconductor material oriented on a tape substrate, wherein the tape substrate and the superconductor material define a first interface therebetween do. The method further includes forming an alloy coating on the superconductor layer, wherein the alloy coating and the superconductor layer define a second interface opposite the first interface, and the alloy coating comprises one or more metal layers And the at least one metal layer comprises a metal alloy.

1 illustrates a current limiting system according to one embodiment;
Figure 2a shows an embodiment of a coated superconducting tape having an alloy coating;
Figure 2b shows a variant of the embodiment of Figure 2a;
Figure 2c shows another variant of the embodiment of Figure 2a;
Figure 3a illustrates one embodiment of a bilayer alloy coating;
Figure 3b illustrates another embodiment of a dual layer alloy coating;
Figure 3c shows a further embodiment of a dual layer alloy coating;
Figure 4a illustrates a scenario for the operation of a coated superconducting tape having a dual layer alloy coating under steady state conditions;
Figure 4b illustrates one scenario for the formation of a conductive oxide in the coated superconductor tape of Figure 4a during a fault condition;
Figure 4c shows another scenario for the formation of a conductive oxide in the coated superconductor tape of Figure 4a during a fault condition;
Figure 5 shows a binary phase diagram for an Ag-Zr system.

The present disclosure will now be described more fully hereinafter with reference to the accompanying drawings, in which certain embodiments are shown. However, the content of this disclosure may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the subject matter to those skilled in the art. In the drawings, like numerals denote like elements throughout the specification.

In order to address some of the deficiencies in the above-mentioned superconductor tapes, embodiments providing improved techniques for forming superconductor tapes as well as improved structures for superconductor tapes are described in the present application. These embodiments may be particularly suitable for applications of superconductor tapes and other applications where the tapes are subject to an AC voltage included in the current limiters.

To address this situation, the embodiments provide superconductor tape structures that include an alloy coating that specifically includes one or more metal alloy layers. In particular, a metal alloy (also referred to herein as simply " alloy ") coating is disposed in contact with the superconductor layer. The alloy layer (s) in the alloy coating, which will be described in detail below, is particularly useful for improved resistance to " burnout " during a fault condition, increased sheet resistance, Lt; RTI ID = 0.0 > superconducting < / RTI >

The term " alloy " as used in this application refers to one or more other elements, such as a metal mixture having one or more additional metal elements. The alloy may be a solid solution of two or more elements forming a single phase; A mixture of two or more phases, each of which may be a solid solution of two or more elements; One or more intermetallic compounds; Or a mixture of any of the above. An intermetallic compound may be a " line " compound in which the proportion of constituent elements is unchanged, but may be a compound in which the proportion of constituent elements varies. In the discussion that follows, examples are presented of how a suitable combination of superconductor tape characteristics can be matched by appropriate selection of alloying elements. The alloy coatings disclosed herein include at least one alloy layer and may include a single alloy layer, a single alloy layer and a further non-alloy layer (s), a plurality of alloy layers and a plurality of non-alloy layers, ≪ / RTI > In embodiments, following the examples of silver or copper layers alloyed with a single element is provided for various alloy elements. However, the embodiments include alloys in which two or more of these alloying elements are alloyed with a material such as copper or silver.

Figure 1 illustrates the architecture of a superconducting fault current limiter (SCFCL) system 100 according to embodiments of the disclosure. The SCFCL system 100 includes a SCFCL 102, which may be a conventional SCFCL, except as noted in this application with respect to the following description. The SCFCL system 100 further includes a protective element 106 containing superconducting tapes arranged in accordance with various embodiments. The SCFCL 102 is arranged in series with a transmission line 108 designed to conduct a load current. Under normal operating mode, the load current may pass periodically, intermittently, or continuously through the SCFCL system 100. The load current in the normal operating mode is such that the load current passing through the superconductor elements 104 having a zero resistance when the superconductor elements 104 remain in the superconducting state and thus the load current passes through the SCFCL 102 Lt; / RTI > Thus, the load current is transmitted with a relatively lower resistance through the SCFCL, which includes resistive points including steady state metals and connection points.

The superconductor elements 104 are fabricated using (HTc) tapes. As background, HTc tapes are used in situations where a device, such as a SCFCL, is cooled, typically at a liquid nitrogen boiling point (77 K) below the critical temperature of the superconductor material used to make the HTc tape. SCFCL transmits electrical current through a superconductor (HTc) tape without resistance when the electric current is less than the critical current (Jc), which is a function of the superconductor material and tape geometry in which the tape is made. Under fault conditions, the electrical current conducted through the SCFCL 102 experiences a surge, exceeds the Jc and converts the superconductor material to a finite state resistance, Detour through layers. In conventional HTc tape structures, the high temperatures released during a failure when current is diverted through metal contact layers include metal atom diffusion, grain growth, thermally induced stress, (s) of the metal layer (s) causing the formation of voids, layer agglomeration, and discontinuities. In addition, depending on the ambient when failure occurs, oxidation of the metal layer may occur. This set of phenomena may also be referred to in this application as " burn out " and may occur after a single fault event or after a number of fault events.

According to these embodiments, the metal coatings used to construct the superconductor elements 104 include at least one alloy layer with improved resistance to burnout. In various embodiments, the alloy layer forms a coated conductor structure portion having metal layers surrounding the inner superconductor layer of the superconductor tape. 2A shows an embodiment of a superconductor tape 200 in which a superconductor layer 204 is disposed on a substrate 202 comprising a plurality of layers as described below. Due to its constituent layers, the substrate 202 forms a template for the growth of a highly oriented superconductor layer. The terms " oriented " or " highly oriented ", as used in the present application, are intended to encompass all types of orientations, such as high bi-axial orientations in which one crystallographic axis lies parallel to a single direction. Refers to a characteristic having a crystallographic orientation. Suitable materials for the superconductor layer 204 include, for example, ReBa ₂ Cu ₃ O _{7 -x} where R is a rare earth element or Bi ₂ Sr ₂ Ca _{n - 1} Cu _n O _{4 + 2n + x} . Each of the materials in these families includes any composition suitable for use in a current limiter in which the critical temperature (TC) of the compositions and the critical current performance are operated at liquid nitrogen temperature. An alloy coating 206 is disposed over the superconductor layer 204 that is configured to conduct a transient fault current that can manifest during current, e.g., a fault condition in which the superconductor layer 204 is switched to a non-superconducting state. The composition and / or microstructure of the alloy coating 206, which will be described in more detail below, is such that the alloy coating 206 has an out-of-phase (or out) appearance over the stack of conventional metal layers or layers used in superconductor tapes such as silver or copper which is more resistant to burnout. In various embodiments, an alloy coating may be applied to the substrate 210 on the opposite side where the superconductor layer 204 is disposed, such that the coating 210, which may extend around the superconductor tape 200 and which may be the same material as the material of the alloy coating 206, (202). This results in a structure in which the superconductor layer 204 and the substrate 202 are surrounded by an alloying material. However, in the following figures, the coating 210 is omitted for clarity.

Figures 2b and 2c superconductor layer 204, these materials YBa ₂ Cu ₃ O ₇ showing a large critical current _- proposes the modification of the superconducting tape _x 200. 2B, the substrate 202 may include a base metal alloy layer 210, a Y ₂ O ₃ layer 212 disposed over the base metal alloy layer 210, a Y ₂ O ₃ layer 212 over the Y ₂ O ₃ layer 212, A deposited yttrium stabilized zirconia (YSZ) layer 214, and a CeO ₂ layer 216 disposed over the YSZ layer 214. Examples of suitable materials for the base metal alloy layer 210, as specifically illustrated in Figures 2b and 2c, include nickel-based alloys such as Hastealloy C-276. However, other metal alloys may also be used. The CeO ₂ layer 216 represents the layer on which the superconductor layer 204 is disposed.

In the example of FIG. 2C, the substrate 202 comprises a base metal alloy layer 210, an Al ₂ O ₃ / Y ₂ O ₃ buffer layer 221, an MgO layer (IBAD MgO 222) formed by ion beam- ), A homoepitaxial MgO layer 224 disposed over IBAD MgO 222, and an epitaxial LaMnO ₃ (LMO) layer 226. The epitaxial LMO layer 226 represents a layer on which the superconductor layer 204 is disposed. In each case, above the oxide layer with the YBa ₂ Cu ₃ O _{7 -x} superconductor layer 204 is-to be able to be axially textured (textured) YBa ₂ Cu ₃ O _7-x superconductor layer of RTI ID = 0.0 > 204 < / RTI > is formed of an epitaxial layer with high threshold current performance. In particular, embodiments are not limited to the specific film stacks shown in Figures 2b and 2c.

In various embodiments, the superconductor tape 200 is designed to support a threshold current as high as about 1000 Amps (A) per centimeter width of the superconductor tape. Referring again to FIG. 2A, the superconductor tape width d _tape reflects the size of the superconductor tape 200 in a direction perpendicular to the direction of current flow in the Y direction with respect to the illustrated Cartesian coordinate system. For a layer thickness of about 1 micrometer (along the Z direction), a critical current of 1000 A / cm width corresponds to a critical current density of 10 ⁷ Amp / cm ² . To support high threshold current performance, the superconductor tape 200 is configured to support a high current surge that can occur during a fault condition. For example, in embodiments where the d- _tape of the superconductor tape 200 is about 1 cm, the current density may be 1000 A (and temporarily higher in the faulted state before the superconductor layer 204 is switched to the non- ), Thereby bypassing the current through the alloy coating 206. Thus, in various embodiments, the alloy coating 206 is designed to withstand current excursions exceeding a minimum of 1000 A.

In some embodiments, the alloy coating 206 is a bilayer stack comprising at least one layer of an alloy. Figures 3a, 3b and 3c illustrate variants of a superconducting tape with an alloy-containing bilayer stack. 3A shows an end cross-sectional view of a superconducting tape 300 including a superconductor layer 304 disposed on a substrate 302. FIG. In this example, the bilayer stack 305 formed on the superconductor layer 304 includes a metal layer 306 disposed over the superconductor layer, not the alloy, and an alloy layer 308 disposed over the metal layer 306. 3B is a cross-sectional end view of a superconducting tape 310 comprising a variant of a bilayer stack 307 formed on a superconductor layer 304 - a metal layer 312 in contact with the superconductor layer 304 - Respectively. The superconducting tape 310 also includes a metal layer 314 disposed over a metal layer 312 that is not an alloy. In Figure 3c, a superconductor tape 320 comprising a variant of a double layer stack 309 formed on a superconductor layer 304 - a metal layer 312 in contact with the superconductor layer 304 is an alloy and the metal layer 312 An alloy layer 308 disposed on top of the alloy layer 308.

The alloy layers shown in Figures 3a-3c according to various embodiments can be made by any convenient method including plating, chemical vapor deposition, or physical vapor deposition. Embodiments are not limited to this situation.

Each of the configurations of the superconductor tapes shown in Figures 3a-3c is otherwise effective to reduce burnout that can occur when an overtemperature is generated on an individual superconductor tape, for example during a fault condition. In some embodiments of the superconductor tape in which the superconductor layer is covered by a bilayer metal structure or alloy coating, the layer inside the dual layer metal alloy coating contacting the superconductor layer is a silver-containing layer and the outer The layer is a copper-containing layer. In typical configurations, the silver-containing layer has a thickness in the range of from a few tens of nanometers to about one micrometer, and the copper-containing layer has a thickness in the range of 5 micrometers to 50 micrometers. The silver-containing layer is effective to maintain a low contact resistance between the superconductor layer and the double layer metal stack. The silver-containing layer is also effective in preventing interdiffusion of the copper-containing layer and the superconductor layer, which can degrade the superconducting properties of the superconductor layer. On the other hand, the copper-containing layer is efficient in delivering most of its fault current, which can be caused by its large thickness and low resistivity of copper.

In some embodiments, the silver alloy layer of the superconductor tape is made of an alloy element that forms a conductive oxide under an oxidizing environment. Examples of such alloy layers are alloys of Ag and Sn or alloys of Ag and Zn. Specifically, in embodiments, typical compositions for such alloys are from about 0.5 mole% to about 30 mole% of either Sn or Zn. At relatively lower concentrations, each of these alloys forms a single phase solid solution with silver. For example, the Ag-Zn binary system forms a single-phase face-centered cubic (fcc) structure when the mole fraction of Zn is less than about 25%, and the Ag-Sn binary system has a mole fraction of Sn of about 15% Form a single phase when small. During a fault condition, high temperatures generated by an excess current in the superconductor tape coupled with an ambient ambient, which typically surrounds the superconductor tape, can result in oxidation of the silver-containing layer. Since each of the Ag-Zn or Ag-Sn alloy layers in these embodiments contains elements that form conductive oxides, any oxidation that occurs within the silver alloy layer will nevertheless result in an acceptable contact resistance with the superficial superconductor layer Lt; RTI ID = 0.0 > a < / RTI >

To illustrate this point, FIGS. 4a-4c present two different scenarios for the oxidation of a silver alloy layer caused by a collective failure state or other conditions that cause heating of the silver alloy layer. A side cross-sectional view of a superconducting tape 400 in which the tape in Figure 4a may include a copper layer, or an upper layer (not shown to scale), e.g., a non-alloyed layer 314 is shown. However, in other embodiments, the copper layer may be an alloy layer. The terms " copper layer " and " silver layer ", as used in this application, unless otherwise specified, mean that the molar fraction of that layer individually is greater than 50% Lt; / RTI > may comprise any individual layer that is larger than the < RTI ID = 0.0 > Thus, the " copper layer " may be pure copper or it may contain one or more additional elements, the total mole fraction of which is less than 50% of the copper layer. The superconducting tape 400 comprises a silver alloy layer 402 which may be formed of Ag-Zn or Ag-Sn solid solution in different embodiments. In particular embodiments, the molar fraction of Zn or Sn in the alloy layer 402 is 30% or less. The superconducting tape 400 operates under steady-state conditions where the ambient is cooled to a cryogenic temperature, e.g., liquid nitrogen temperature (77 K). The electrical current 404 is transmitted through the superconductor tape 400 at a current level below Jc so that the superconductor layer 304 is in a superconducting state and the electrical current 404 is superconducting along the longitudinal direction Lt; RTI ID = 0.0 > 304 < / RTI > Under these conditions, the electrical current 404 traverses the superconductor layer 304 without resistance and little or no resistive heating occurs within the superconductor tape 400.

In FIG. 4B, a fault condition occurs in which an excess current turns the superconductor layer 304 into a non-superconducting state, so that the electric current 406 is conducted in the copper layer 314 and partly in the silver layer. The electric current 406 is sufficient to generate resistive heating so that the superconductor tape 400 reaches the elevated temperature. In some instances, the superconducting tape 400 may reach 300 [deg.] C, 400 [deg.] C, or even higher. This elevated temperature causes oxidation of the silver layer that produces the oxidized layer 408. Since the silver alloy layer 402 contains tin or zinc, the oxidized layer 408 remains electrically conductive and has a contact resistance that is particularly acceptable at the interface 410. Although silver itself is capable of forming conductive oxides, the addition of tin or zinc may facilitate formation of a more conductive layer.

In FIG. 4C, there is shown another scenario in which a fault condition occurs for the structure of FIG. 4A and the electric current 406 is conducted in the copper layer 314 and partly in the silver layer. In this example, the resulting elevated temperature during a fault condition is generated from the interface oxide layer 412 in addition to the original silver alloy layer 402, residual layer 414. The interfacial oxide layer 412 may include a Sn-rich oxide layer, alternatively a Zn-rich oxide layer, wherein the Sn content or, alternatively, the Zn content, is higher than in the residual layer 414. [ The interfacial oxide layer 412 may exhibit a low contact resistance so that the superconducting tape 400 can be prevented from reaching the superconductor layer 304 at an event where the electrical current enters or exits the faulted state, ) And the copper layer 314 as shown in Fig. The scenario of Figure 4b or 4c may be helpful, depending on the molar fraction of silver and Sn or Zn used, as well as the exact fault conditions. In either case, the silver alloy layer provides a more robust material that can withstand oxidation events and maintain acceptable conductive properties.

In further embodiments, the silver alloy layer of the superconductor tape is made of an alloy element that forms a precipitate in the silver alloy layer. These precipitates can be effective to maintain the stability of the silver alloy layer under the high temperature conditions (> 250 [deg.] C) that occur during the failure state. In particular embodiments, alloying elements are selected based on the tendency to form silver and intermetallic compounds - the compounds may tend to separate into precipitates under certain conditions. In one example, Au-Zr alloy layers are formed for Zr molar concentrations of up to about 25%. Figure 5 shows a portion of a binary equilibrium phase diagram for an Ag-Zr system. For a molar concentration below 50% Zr, a pure silver phase and two phase regions made of a binary AgZr compound may be present. Thus, at lower concentrations of Zr (< 25%), the AgZr phase can be expected to separate into isolated regions, for example, in grain boundary precipitates on a silver matrix. When these microstructures are formed, the AgZr precipitates act to fix the grain growth of the silver particles in the matrix phase when the Ag-Zr alloy layer is subjected to elevated temperatures. This helps to keep the Ag-alloy layer under a raised temperature at a smooth layer and thereby reduces the tendency to agglomerate into a layer.

In further embodiments of the alloy layer, the superconducting tape is added to silver, which alloying elements are effective in improving the properties of the underlying superconductor layer. In some embodiments, Zr or Ta is added to silver at a molar concentration of about 0.5% to 10% to form a metal alloy layer. Embodiments are not limited to this situation.

During the fabrication of the superconductor tape, when a silver alloy layer containing Zr or Ta is initially formed on the superconductor layer, Zr or Ta may be dispersed in a silver matrix, such as an intermetallic compound, as mentioned above have. Superconductor tape is then elevated temperature - for example, one seconds or about 300 ℃ for more - when dependent on, Zr or Ta is not at least the (underlying) superconductor layer, for example, _{YBa 2 Cu 3 O 7 -x (} YBCO) layer portion and And can form an effective precipitate phase, such as ZrBaO _x or TaBaO _x , to generate a flux that fixes the centers in the superconductor layer. Flux pinning is a phenomenon in which magnetic flux lines are not moving (trapped, or "pinned") despite the Lorentz force acting on the magnetic flux lines inside the electrical current delivered to the superconductor. ) ") Phenomenon. Flux pinning does not occur in Type I superconductors but occurs in Type II superconductors such as YBCO. In particular, flux pinning occurs, for example, when there are crystallographic defects resulting from grain boundaries of impurities. Flux peening is a "flux creep" that can create pseudo-electrical resistance in a superconductor layer and can reduce the critical current density and critical field that convert the superconductor layer to a non-superconducting state. May be desirable in high temperature ceramic superconductor materials. Thus, in various embodiments, when the silver alloy layer containing Zr or Ta is subjected to a temperature above 300 ° C, for example during a failure event or due to intentional annealing of the silver alloy layer, The flux pinning properties of Type II oxide superconductors can be improved.

In other embodiments, alloying elements or elements are added to the copper layer, and the alloying elements are effective to reduce copper layer grain growth, roughening, and / or agglomeration. Examples of efficient alloying elements are Sn, Zn and other elements forming copper and solid solutions; And Zr, Ta, and other elements capable of forming precipitate phases. The choice of alloying elements may be based in part on the desired resistivity of the copper layer achieved by the alloying elements. For example, the addition of elements that form copper and solid solutions can result in relatively less increase in resistance in comparison to pure copper layers, while the addition of elements that form precipitates Can produce a relatively larger increase in resistance.

The addition of alloying elements in various embodiments is efficient in increased engineering in sheet resistance in the metal layer (s) disposed on the superconductor layer of the superconductor tape. This is useful for increasing the voltage drop per unit length of the superconductor tape and thereby reducing the length of the superconductor tape required in a given SCFCL. The incorporation of alloying elements in the copper layer of a copper / silver bilayer system can be effective in increasing sheet resistance in two ways. It should be noted that, in the first situation, the copper overlayer may be several times thicker than an underlayer in contact with the superconductor layer. In some tape structures, for example, the copper layer may have a thickness of about 20 micrometers and the silver layer may have a thickness of 1 micrometer. Therefore, the sheet resistance of the Cu / Ag stack depends on the sheet resistance of the copper upper layer, since pure copper and pure silver have similar resistivities. With this in mind, alloying elements such as Zr are added to increase the resistivity of the upper copper layer in various embodiments.

Secondly, due to the increased resistance to agglomeration or other undesirable layer changes added to the upper copper layer when alloying with certain elements such as Zr, the overall layer thickness of copper in the superconductor tape in further embodiments can be reduced have. For example, in some embodiments, a copper alloy having a thickness of 10 micrometers may be used as the top layer to conduct the fault current in the superconductor tape. A 10 micrometer thick copper alloy layer undergoes aggregation or roughening under high temperature conditions that are effective to roug a thicker layer, such as a 20 micrometer thick pure copper film, in addition to an appropriate amount of Zr, such as from about 10 percent to about 20 percent. It can withstand.

In various further embodiments, the copper / silver bilayer system is comprised of both a copper alloy and a silver alloy. The alloying elements of each layer can be adjusted to optimize the desired combination of coating properties. In some embodiments, more than one element may be added to an individual copper or silver layer. For example, zirconium is added to improve flux pinning in the underlying superconductor layer, although alloying elements such as tin may be added to optimize conductivity at the interface.

In summary, these embodiments provide a superconducting tape constructed with a single layer or multilayer metal alloy coating for improved tape properties, including resistance to degradation during failure conditions. In some embodiments, the metal alloy coating provides additional performance advantages, such as increased voltage drop per unit tape length and improved flux pinning in the superconductor layer of the base. The superconductor tapes of the present embodiments can be made using a variety of techniques including those techniques for making metal coatings on conventional superconducting tapes.

The invention is not to be limited in scope by the specific embodiments described herein. Rather, in addition to those embodiments described herein, various other embodiments of the invention and modifications thereto will be apparent to those skilled in the art from the foregoing description and the accompanying drawings. Therefore, such other embodiments and modifications are intended to fall within the scope of the disclosure of the present invention. Furthermore, although the present invention has been described herein in the context of a particular implementation in a particular environment for a particular purpose, those skilled in the art will readily appreciate that the utility of the invention is not so limited, &Lt; / RTI &gt; may be beneficially implemented within the environment. Accordingly, the claims set forth below should be understood in terms of the full effect and idea of the invention as described herein.

Claims (15)

In a superconductor tape,
A substrate comprising a plurality of layers;
An oriented superconductor layer disposed on the substrate; And
An alloy coating disposed over the superconductor layer, wherein the alloy coating comprises one or more metal layers and the at least one metal layer comprises a metal alloy. The superconductor tape according to claim 1, wherein the superconductor layer comprises RBa ₂ Cu ₃ O _{7 - x} , wherein R is a rare earth element. The superconductor tape of claim 1, wherein the alloy coating comprises a copper layer / silver layer bilayer structure. 4. The superconductor tape according to claim 3, wherein the copper layer comprises a Cu alloy and has a thickness of 10 [mu] m or less. 4. The superconductor tape according to claim 3, wherein the silver layer comprises an Ag alloy. 5. The superconductor tape according to claim 4, wherein the copper alloy comprises a mixture of copper and zirconium, copper and tin, or copper and zinc. 7. The superconductor tape of claim 6 comprising a mixture of zirconium and copper having a mole fraction of zirconium of 10% or less. The superconductor tape according to claim 5, wherein the Ag alloy comprises Zr or Ta, and the Zr or Ta has a molar fraction between 0.5 and 10.0%. 9. The device of claim 8, wherein the superconductor layer
RBa ₂ Cu ₃ O _{7 -x} , wherein R is a rare earth element; Wherein the Ag alloy is effective to produce Zr-containing oxide precipitates or Ta-containing oxide precipitates when the superconducting tape is heated to 300 DEG C or higher for about one second or more. The superconductor tape according to claim 5, wherein the Ag alloy comprises Sn or Zn, and the Sn or Zn has a molar fraction between 0.5 and 30%. A method for forming a superconductor tape,
Forming a superconductor layer comprising a superconductor material oriented on a tape substrate, said tape substrate and superconductor material defining a first interface therebetween; forming said superconductor layer; And
Forming an alloy coating on the superconductor layer, the alloy coating and the superconductor layer defining a second interface opposite the first interface, the alloy coating comprising one or more metal layers and the at least one metal layer &Lt; / RTI &gt; wherein the metal alloy comprises a metal alloy. 12. The method of claim 11, wherein forming the alloy coating comprises:
Forming a silver layer on the superconductor layer; And
Forming a copper layer over the silver layer, wherein the silver layer is disposed between the copper layer and the superconductor layer. The method according to claim 11, wherein the superconductor layer is RBa ₂ Cu ₃ O _{7 -} including but _x, R is a rare earth element, the method. 13. The method of claim 11, wherein forming the superconductor layer comprises forming a Type II superconductor comprising a copper oxide based superconductor, the method comprising: providing a metal alloy layer of an alloy coating in contact with the superconductor layer; Wherein the alloy element in the metal alloy layer is efficient to react to form an oxide precipitate in the superconductor layer when the superconductor tape is heated to 300 占 폚 for one second or more. 12. The method of claim 11 comprising forming the copper layer as a Cu alloy and forming the silver layer as an Ag alloy.

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